Time calibration method and related apparatus

Abstract

A time calibration method includes a first station receives a first frame from a second station; the first station stores a receiving moment of the first frame; the first station receives a second frame from the second station, where the second frame includes a sending moment at which the second station sends the first frame; and the first station obtains a clock offset between a first clock of the first station and a second clock of the second station based on the receiving moment of the first frame and the sending moment of the first frame.

The invention claimed is: 
     
       1. A method implemented by a first station for obtaining a clock offset between a first clock of the first station and a second clock of a second station, the method comprising:
 receiving a first frame from the second station without establishing a fine timing measurement (FTM) session between the first station and the second station, wherein the first frame comprises a first sequence number; 
 storing the first sequence number and a receiving moment of the first frame; 
 receiving a second frame from the second station, wherein the second frame comprises a second sequence number and a sending moment at which the second station sends the first frame; 
 retrieving the receiving moment based on the second sequence number; and 
 obtaining a clock offset between a first clock of the first station and a second clock of the second station based on the receiving moment and the sending moment. 
 
     
     
       2. The method according to  claim 1 , wherein the second sequence number is the same as the first sequence number. 
     
     
       3. The method according to  claim 2 , further comprising storing an identifier of the second station. 
     
     
       4. The method according to  claim 2 , wherein retrieving the receiving moment based on the second sequence number comprises searching for the receiving moment corresponding to the second sequence number. 
     
     
       5. The method according to  claim 1 , wherein the second sequence number is greater than the first sequence number by one, and wherein retrieving the receiving moment based on the second sequence number comprises:
 subtracting one from the second sequence number to obtain the first sequence number; and 
 searching for the receiving moment corresponding to the first sequence number. 
 
     
     
       6. The method according to  claim 1 , wherein the second station is an access point, and wherein the first frame and the second frame are beacon frames. 
     
     
       7. The method according to  claim 1 , wherein the receiving moment is when the first frame arrives at a physical layer component in the first station. 
     
     
       8. The method according to  claim 1 , wherein the receiving moment is when a training field in a preamble of the first frame arrives at a physical layer component in the first station. 
     
     
       9. The method according to  claim 1 , wherein obtaining the clock offset comprises obtaining the clock offset between the first clock and the second clock through calculation based on a hardware time delay of the first station, the receiving moment, and the sending moment. 
     
     
       10. The method according to  claim 1 , wherein the first frame and/or the second frame further comprise/comprises first level information indicating a first level of the second station, and wherein the method further comprises:
 obtaining second level information indicating a second level of the first station; and 
 following time of the second station based on the clock offset when the first level is higher than the second level. 
 
     
     
       11. The method according to  claim 6 , wherein the sending moment of the first frame is located in a vendor-defined element of the second frame. 
     
     
       12. A first station comprising:
 a memory configured to store instructions; and 
 one or more processors coupled to the memory and configured to execute the instructions to cause the first station to:
 receive a first frame from a second station without establishing a fine timing measurement (FTM) session between the first station and the second station, wherein the first frame comprises a first sequence number; 
 store the first sequence number and a receiving moment of the first frame; 
 receive a second frame from the second station, wherein the second frame comprises a second sequence number and a sending moment at which the second station sends the first frame; 
 retrieve the receiving moment based on the second sequence number; and 
 obtain a clock offset between a first clock of the first station and a second clock of the second station based on the receiving moment and the sending moment. 
 
 
     
     
       13. The first station according to  claim 12 , wherein the second station is an access point, and the first frame and the second frame are beacon frames. 
     
     
       14. The first station according to  claim 12 , wherein the receiving moment is when the first frame arrives at a physical layer component in the first station. 
     
     
       15. The first station according to  claim 12 , wherein the receiving moment is when a training field in a preamble of the first frame arrives at a physical layer component in the first station. 
     
     
       16. The first station according to  claim 12 , wherein the first frame and/or the second frame further comprise/comprises first level information indicating a first level of the second station, and wherein the one or more processors are is further configured to execute the instructions to cause the first station to:
 obtain second level information indicating a second level of the first station; and 
 follow time of the second station based on the clock offset when the first level is higher than the second level. 
 
     
     
       17. The first station according to  claim 12 , wherein the second sequence number is the same as the first sequence number. 
     
     
       18. The first station according to  claim 17 , wherein the one or more processors are further configured to execute the instructions to cause the first station to retrieve the receiving moment based on the second sequence number by searching: for the receiving moment corresponding to the second sequence number. 
     
     
       19. The first station according to  claim 17 , wherein the second sequence number is greater than the first sequence number by one, and wherein the one or more processors are further configured to execute the instructions to cause the first station to retrieve the receiving moment based on the second sequence number by:
 subtracting one from the second sequence number to obtain the first sequence number; and 
 searching for the receiving moment corresponding to the first sequence number. 
 
     
     
       20. A non-transitory computer-readable storage medium storing program code, the program code comprising instructions, which when executed using a one or more processors of a first station cause the first station to:
 receive a first frame from a second station without establishing a fine timing measurement (FTM) session between the first station and the second station, wherein the first frame comprises a first sequence number; 
 store the first sequence number and a receiving moment of the first frame; 
 receive a second frame from the second station, wherein the second frame comprises a second sequence number and a sending moment at which the second station sends the first frame; 
 retrieve the receiving moment based on the second sequence number; and 
 obtain a clock offset between a first clock of the first station and a second clock of the second station based on the receiving moment and the sending moment.